Running the Cognate tests I get:
1) Cognate\Tests\CognateIntegrationTest::testCreateDeleteAndRestorePageResultsInEntry InvalidArgumentException: The given Title does not belong to page ID 2 but actually belongs to 4 includes/Storage/RevisionStoreRecord.php:99 includes/Storage/RevisionStore.php:586 includes/Storage/RevisionStore.php:476 includes/libs/rdbms/database/Database.php:3731 includes/Storage/RevisionStore.php:478 includes/page/PageArchive.php:776 includes/page/PageArchive.php:506 extensions/Cognate/tests/phpunit/CognateIntegrationTest.php:97 tests/phpunit/MediaWikiTestCase.php:469 maintenance/doMaintenance.php:94
Found locally with SQLite as a backend and the experimental CI job quibble-vendor-mysql-php70-docker fails similarly (eg on https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Cognate/+/447052/ ).
Reproducible on a dummy change https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Cognate/+/442292/